1. Field of the Invention
This invention relates to polymerized films and a process for making the same. More particularly, it relates to a plasma-polymerized film which is formed by depositing and polymerizing a metal element-containing material forming an electrode and a gaseous polymerizable carbon-containing reactant.
This invention also relates to members for use with media capable of recording and/or reproduction of information utilizing magnetism, light or the like, for example, casings or cartridges for video tape, audio tape and computers, the members having a polymerized film as a surface coating, and a process for making the same.
2. Discussion of Prior Art
Technology utilizing polymerized films, especially thin films has been of increasing importance in these days. A variety of processes are available to form thin films. Among others, a vacuum thin film forming process is one of the most important techniques critical in the information, electron, watch and optical (such as camera) industries. Great research efforts have been made on thin films and their preparation as well as their application, and new films and processes have been continuously developed.
Among various films, plasma-polymerized films draw attention to their excellent film properties and are used in a variety of applications. However, since organic gases are generally used as the reactant gas to form such plasma-polymerized films, the resulting films are organic films which are believed difficult to modify their properties as by imparting electric conductivity.
The inventors proposed to form a plasma-polymerized, metal-containing film using a gaseous organometallic monomer as reactant gas (see Japanese Patent Application Kokai No. 222115/1983).
The film is a modified film in that antistatic and other properties are imparted to a conventional plasma-polymerized film. However, the reactant used in this process is not necessarily available in plenty and it is difficult to change the ratio of carbon to metal in the reactant as desired. The type and content of metal in the thin film are somewhat limited. It is less feasible to change the basic nature, typically electric conductivity and antistatic function of the thin film as desired.
Japanese Patent Application Kokai No. 88829/1983 proposes a magnetic recording medium comprising a polymerized, metal-containing, carbon fluoride base film and a method for making the same.
According to the disclosure, a medium having a protective film having improved durability and corrosion resistance is provided as well as its preparation. However, it is difficult to increase the content of metal element in a film under conditions within the range described in the disclosure (that is, W/(F.multidot.M).apprxeq.10.sup.7 Joule/kg as later defined) until electric conductivity is imparted to the film, and it is also difficult to change the metal element content as desired.
Generally speaking, various information recording/reproducing carriers including video cassettes, audio cassettes, computer cartridges, video floppy disks, and laser vision disks are of the design that a tape or disk-shaped recording/reproducing medium is received in a casing such that the medium may travel or rotate in the casing or recording/reproducing equipment. More particularly, within these recording/reproducing carriers, the recording/reproducing medium moves in sliding contact with members constructing the casing, and members in the casing make mutual slide contact during movement.
In the case of video tape cassettes, for example, the cassette casing has received therein a recording medium in the form of video tape and various members including reels on which the tape is wound, brakes for locking the reels, and guide posts and tape guides for guiding the tape during operation.
When the recording/reproducing equipment is loaded with the medium and operated, the video tape makes slide contact with the tape travel guide members such as guide posts and tape guides, and the reels make contact with reel-retaining leaf springs.
To ensure that the travel or rotation of the medium in the form of tape or disk be accurate, smooth and stable, these members have to meet the following requirements:
(A) a low coefficient of friction, PA1 (B) sufficient abrasion resistance and surface hardness to minimize abrasion of the members and the tape which would cause dropouts, and PA1 (C) antistatic properties to prevent static electrification which would cause recording/reproducing malfunctions.
In the prior art, these members are formed from resinous material because of ease of molding and lightweight and they are provided with antistatic coatings on the surface, replaced by abrasion resistant metal parts for the necessary portions, or provided with metal coatings.
However, formation of an antistatic coating has problems including difficulty of coating a uniformly thin film and blooming. Partial replacement of the members by metal parts has problems including an increased number of steps, increased cost, and difficulty of processing a complex shape.
Under the circumstances, the inventors previously proposed to form a plasma-polymerized film of organometallic compound (Japanese Patent Application Kokai No. 222115/1983) and silicon compound (Japanese Patent Application Kokai No. 222438/1983) on such members.
For these films, nevertheless, only antistatic property is taken into account while no evaluation is made on friction during operation.